Objective: To determine the related substances in dienestrol tablets by HPLC. Methods: The separation was performed on a C18column( 250 mm × 4. 6 mm,5 μm). The mobile phase consisted of methanol-acetonitrile( 76∶ 24),the flow rate was set at 0. 8ml·min- 1with the detection wavelength at 229 nm,and the sample size was 10 μl. Results: Under the established chromatographic conditions,the related substances and dienestrol were separated completely. The limit of detection was 2 ng. Conclusion: The method is simp...